System for connecting rotary kiln for treating materials to an installation for preheating the materials via the gases leaving the kiln



1970 I BQVAGNE ETAL 3,537,693

j 1 I a SYSTEM FOR'CONNECTING ROTARY KILN FOR TREATING MATERIALS TO AN INSTALLATION FOR PREHEATING THE MA'llINIM-S VIA THE GASES LEAVING THE KILN Filed Sent. 16, 1968 FIG. 2

% Inf I \9 I I United States Patent Int. Cl. F27b 7/00 US. Cl. 263-33 3 Claims ABSTRACT OF THE DISCLOSURE A rotary kiln from which extends a duct for connecting gases from the kiln to a preheater and to which is coupled a device for feeding preheated material, the device outlet being in the kiln and below the lower edge of the .duct at the kiln.

Theinvention relates to a system for connecting a rotary kiln for treating materials to an installation for preheating'the materials via the gases leaving the kiln, the system being used more particularly in cement-producing installations.

Installations for preheating the raw materials are known which comprise a series of separators connected by ducting in which the materials, which circulate in counter-current with the gases leaving the kiln, are successively brought into contact with the gases and then separated therefrom, so that the materials reach a temperature close to that of the gases leaving the kiln at the moment when the materials are introduced thereinto.

As a rule, disposed at the outlet from the kiln is a smoke box which guides the gases towards the preheater inlet conduit. The materials are introduced into the smoke box and descend along the inclined end thereof as far as the kiln inlet. Sometimes the feed conduit for the materials is continued so as to pour the materials directly into the kiln.

The smoke box is as a rule a simple connection chamber through which the gases flow which are then accelerated in the preheater ducting. -Most frequently no attempt has been made to improve the flow of the gases the result being dead zones in which the gases have a reduced speed, and in which the briquetting temperature is lower. The volatile materials contained in the gases have a tendency to become condensed on the cool portions and to fix the dust entrained by the gases, thus necessitating periodical cleaning.

To obviate this disadvantage, according to the invention, there is disposed at the kiln outlet a chamber for evacuating the gases which encourages their flow from the kiln outlet to the preheater inlet, by accelerating the gases from the kiln outlet onwards and keeping their speed identical at all places. However, the gas flow thus accelerated from the kiln inlet onwards might cause the risk that materials poured into the kiln by the feed device might be entrained into the outlet conduit. This is the reason why measures must be taken not to pour out the materials opposite the kiln outlet aperture.

According to the invention the chamebr for evacuating the gases is formed by substantially cylindrical elongated ducting disposed in the continuation of the outlet aperture for the kiln gases, and having at its two ends members for connecting it respectively to the end hood of the kiln and the inlet ducting of the gases to the preheater, the outlet aperture of the device feeding the materials being disposed inside the kiln, at a lower level than the lower edge of the outlet aperture of the kiln. An exemplary embodiment of the invention will now be described in greater detail, with reference to the drawings, wherein:

FIG. 1 illustrates diagrammatically the system according to the invention, sectioned along the line I-I in FIG. 3;

FIG. 2 is a section, taken along the line 11-11 in FIG. 3, the feed device being removed, and

FIG. 3 is a section, taken along the line III-III in FIG. 1.

A rotary kiln 1 terminates in an end 2 formed with a circular aperture 3. The end of the kiln 1 engages in a fixed hood 4 having a joint 5 ensuring sealing-tightness between the kiln and the hood. The raw materials treated in the kiln are heated, before their arrival in the kiln, in a known preheating installation by the hot gases leaving the kiln. Only the start of the ducting 6 and the last separator 7 of the known preheating installation are show in FIG. 1. According to one feature of the invention, the ducting 6 is connected to the kiln outlet aperture 3 via an elongated cylindrical ducting 8 connected to the hood 4 and to the ducting 6 by connecting members 9 and 10 respectively.

The feed device comprises a collar which extends through the wall of the ducting 8 and in which outlet duct 12 of the separator 7 discharges, and a tube 13 which is closed in its upper portion and slides inside the collar 11. The materials descending from the separator 7 via the duct '12 drop into the tube 13 through an oblong aperture 14 therein. It is therefore possible to regulate the height of the pouring aperture 15 is relation to the wall 1 of the kiln, by changing the position of the tube in the collar. The ducting 8 has a diameter which is substantially smaller than that of the kiln, so that the gases are accelerated as soon as they leave the kiln and are channelled in the direction of the ducting 6. This is why the height of the tube 13 is so regulated that the aperture 15 is disposed substantially lower than the lower edge of the connecting member 9, and pours the materials as close as possible to the pile 16 formed by the materials entrained in the kiln. To this end, the end of the tube is cut in a plane substantially parallel with the pile formed by the materials in normal operating conditions. The outlet aperture is therefore outside the gas flow sucked into the ducting 8, and there is no risk that the materials will be entrained into this flow. Moreover, the connecting member 9 can be continued by a semi-cylindrical collar portion 17 which extends into the kiln as far as the tube 13 and is formed with a central groove for the passage of the tube.

The system can be used more particularly in preheating installations in which gases are recycled in a circuit adapted to regulate heat-exchangers. To this end the Wall of the ducting 8 is formed with two apertures 18 which are disposed on either side of the vertical plane of symmetry of the ducting and through which two conduits 19 extend which are connected to ducting 20 for feeding recycling gas taken at a place in the preheating circuit. The conduits 19 are directed towards the aperture 3 and converge at a point situated substantially on the axis of the ducting 8, adjacent its inlet. The blowing in of the recycling gases is therefore performed in counter-current with the gases leaving the kiln. Mixing is therefore rapidly performed from the ducting inlet onwards and in its axis.

In this way the wall of the ducting is in contact only with gases at a regular temperature, and therefore has no zones of varying temperature, outside the apertures 18. The apertures 18 are disposed in the upper portion of the ducting, so that any accretions which might be formed by concentration are entrained by the gases.

For the material arriving at the inlet of the ducting 6 by means of a distributing device 21 to be entrained by the gases at regular temperature, the flow of recycling gases is regulated in relation to the mean temperature of the gases in the ducting 8. To this end, a register 22 is disposed in the ducting 20 upstream of the conduits 19, the register 22 being controlled by a control device 23 which measures the temperature of the gases at a place 24 disposed at the outlet of the ducting 8.

A narrowed portion 25 disposed at the outlet of the ducting 8 upstream of the connecting member 10 enables the gases to have a speed adequate to entrain the materials poured out by the distributor 21. The ducting 8 can also comprise a register for insulating the preheater (not shown), which is disposed downstream of a branching aperture in the direction of a chimney used more particularly for lighting the kiln. Any materials which may accumulate in the end of the hood 4 are picked up in known manner by scoops 26 which are rotated by the kiln and deliver such materials in front of the inlet of the ducting 8; the gas flow then entrains the materials to the ducting 6 of the separator 7, which returns them to the kiln. The sucking of the dust into the ducting prevents the contamination of the hood at the end of the kiln.

Of course, the invention is not limited to the detailed embodiment described hereinbefore. More particularly, the evacuation ducting or the tube for feeding the materials can have any further device for measuring the temperature or flow of the gases and materials, to regularise the feed and preheating of the materials. Moreover, devices for taking samples of the gas enabling kiln operation to be controlled could be installed at certain places.

What is claimed is:

1. A system for connecting a rotary kiln for the treatment of materials to an installation for preheating the materials by the gases leaving the kiln, the connecting system comprising a chamber for evacuating the gases leaving the kiln to the preheating installation, and a device for feeding to the kiln the materials coming from the preheating installation, the chamber for evacuating the gases being formed by substantially cylindrical elongated ducting disposed in the continuation of the outlet aperture for the kiln gases, and having at its two ends members for connecting it respectively to the end hood of the kiln and the inlet ducting of the gases to the preheater, the outlet aperture of the device feeding the materials being disposed inside the kiln, at a lower level than the lower edge of the outlet aperture of the kiln, the device for feeding the materials comprising a collar which is attached to the end of the outlet duct of the last separator of the preheater and extends through the Wall of the evacuation ducting, and a tube which is closed at its upper portion and which is adapted to slide in the collar and extends as far as the inside of the kiln, the tube being formed with an oblong aperture for the passage of the materials coming from the outlet duct of the separator.

2. A connecting system as set forth in claim 1, the member for connecting the evacuation ducting to the end hood comprising a semi-cylindrical collar portion which is attached to the lower edge of the ducting and is continued into the kiln inlet aperture, said collar portion having a central groove for passage of said tube.

3. A connecting system as set forth in claim 1, characterised in that the end of the tube for feeding the materials is cut to a bevel in accordance with a plane substantially parallel with the surface of the pile formed by the materials entrained inside the kiln under normal operating conditions.

References Cited UNITED STATES PATENTS 3,012,765 12/1961 Deussner 263-32 3,042,389 7/1962 Gieskieng 263-32 3,317,201 5/1967 Muller et al. 263-32 EDWARD G. FAVORS, Primary Examiner 

